+------+    +------+    +------+
          |  CA  |    |  CA  |    |  CA  |
          +------+    +------+    +------+
              |           |           |    Publication protocol
              |           |           |    business relationship
              +-------+   |  +--------+      perhaps set up by
                      |   |  |                    RFC 8183
                 +----v---v--v-----+
                 |                 |
                 |   Publication   |
                 |   Repository    |
                 |                 |
                 +-----------------+     Distribution protocols
                          |                   rsync or RRDP
           +--------------+----------------+
           |              |                |
   +-------v-----+ +------v------+  +------v------+
   |   Relying   | |   Relying   |  |   Relying   |
   |    Party    | |    Party    |  |    Party    |
   +-------------+ +-------------+  +-------------+
      

        +---------------------------------------------------------+
        |     +-----------------+                                 |
        |     |   Secure_Path   |                                 |
        |     +-----------------+                                 |
        |     |    pCount X     |                                 |
        |     |    Flags X      |                                 |
        |     |    AS X         |                                 |
        |     |    pCount Y     |                                 |
        |     |    Flags Y      |                                 |
        |     |    AS Y         |                                 |
        |     |      ...        |                                 |
        |     +-----------------+                                 |
        |                                                         |
        |   +---------------------+     +---------------------+   |
        |   |  Signature_Block 1  |     |  Signature_Block 2  |   |
        |   +---------------------+     +---------------------+   |
        |   |  Algorithm Suite 1  |     |  Algorithm Suite 2  |   |
        |   |  SKI X1             |     |  SKI X2             |   |
        |   |  Signature X1       |     |  Signature X2       |   |
        |   |  SKI Y1             |     |  SKI Y2             |   |
        |   |  Signature Y1       |     |  Signature Y2       |   |
        |   |       ...           |     |       ....          |   |
        |   +---------------------+     +---------------------+   |
        |                                                         |
        +---------------------------------------------------------+
      

                                       64505
                                       |
             ISP B                     ISP A
   CE-1 <--- PE-1 <------------------- PE-2 <--- CE-2
   64496     Old_ASN: 64510   Old_ASN: 64500     64499
      

                                     64505
                                     |
           ISP A'                    ISP A'
 CE-1 <--- PE-1 <------------------- PE-2 <--- CE-2
 64496     Old_ASN: 64510   Old_ASN: 64500     64499
           New_ASN: 64500   New_ASN: 64500
      

                                    64505
                                    |
          ISP A'                    ISP A'
CE-1 ---> PE-1 -------------------> PE-2 ---> CE-2
64496     Old_ASN: 64510   Old_ASN: 64500     64499
          New_ASN: 64500   New_ASN: 64500
      

   0          8          16         24        31
   .-------------------------------------------.
   | Protocol |   PDU    |                     |
   | Version  |   Type   |     Session ID      |
   |    1     |    0     |                     |
   +-------------------------------------------+
   |                                           |
   |                Length=12                  |
   |                                           |
   +-------------------------------------------+
   |                                           |
   |               Serial Number               |
   |                                           |
   `-------------------------------------------'
      

   0          8          16         24        31
   .-------------------------------------------.
   | Protocol |   PDU    |                     |
   | Version  |   Type   |     Session ID      |
   |    1     |    1     |                     |
   +-------------------------------------------+
   |                                           |
   |                 Length=12                 |
   |                                           |
   +-------------------------------------------+
   |                                           |
   |               Serial Number               |
   |                                           |
   `-------------------------------------------'
      

   0          8          16         24        31
   .-------------------------------------------.
   | Protocol |   PDU    |                     |
   | Version  |   Type   |         zero        |
   |    1     |    2     |                     |
   +-------------------------------------------+
   |                                           |
   |                 Length=8                  |
   |                                           |
   `-------------------------------------------'
      

   0          8          16         24        31
   .-------------------------------------------.
   | Protocol |   PDU    |                     |
   | Version  |   Type   |     Session ID      |
   |    1     |    3     |                     |
   +-------------------------------------------+
   |                                           |
   |                 Length=8                  |
   |                                           |
   `-------------------------------------------'
      

   0          8          16         24        31
   .-------------------------------------------.
   | Protocol |   PDU    |                     |
   | Version  |   Type   |         zero        |
   |    1     |    8     |                     |
   +-------------------------------------------+
   |                                           |
   |                 Length=8                  |
   |                                           |
   `-------------------------------------------'
      

   Cache                         Router
     ~                             ~
     | <----- Reset Query -------- | R requests data (or Serial Query)
     |                             |
     | ----- Cache Response -----> | C confirms request
     | ------- Payload PDU ------> | C sends zero or more
     | ------- Payload PDU ------> |   IPv4 Prefix, IPv6 Prefix,
     | ------- Payload PDU ------> |   or Router Key PDUs
     | ------- End of Data ------> | C sends End of Data
     |                             |   and sends new serial
     ~                             ~
      

   Cache                         Router
     ~                             ~
     | -------- Notify ----------> |  (optional)
     |                             |
     | <----- Serial Query ------- | R requests data
     |                             |
     | ----- Cache Response -----> | C confirms request
     | ------- Payload PDU ------> | C sends zero or more
     | ------- Payload PDU ------> |   IPv4 Prefix, IPv6 Prefix,
     | ------- Payload PDU ------> |   or Router Key PDUs
     | ------- End of Data ------> | C sends End of Data
     |                             |   and sends new serial
     ~                             ~
      

   Cache                         Router
     ~                             ~
     | <------ Serial Query ------ | R requests data
     | ------- Cache Reset ------> | C cannot supply update
     |                             |   from specified serial
     | <------ Reset Query ------- | R requests new data
     | ----- Cache Response -----> | C confirms request
     | ------- Payload PDU ------> | C sends zero or more
     | ------- Payload PDU ------> |   IPv4 Prefix, IPv6 Prefix,
     | ------- Payload PDU ------> |   or Router Key PDUs
     | ------- End of Data ------> | C sends End of Data
     |                             |   and sends new serial
     ~                             ~
      

   Cache                         Router
     ~                             ~
     | <------ Serial Query ------ | R requests data
     | ---- Error Report PDU ----> | C No Data Available
     ~                             ~

   Cache                         Router
     ~                             ~
     | <------ Reset Query ------- | R requests data
     | ---- Error Report PDU ----> | C No Data Available
     ~                             ~
      

     Algorithm   Digest          Signature       Specification
     Suite       Algorithm       Algorithm       Pointer
     Identifier
   +------------+---------------+--------------+-----------------------+
   | 0x02-0xF6  | Unassigned    | Unassigned   |                       |
   +------------+---------------+--------------+-----------------------+
      

   +-------+----------------------+-----------+
   | Value | Description          | Reference |
   +=======+======================+===========+
   | 6     | BGP Extended Message | RFC 8654  |
   +-------+----------------------+-----------+